Integrated packer and fluid cross-over subassembly for gas injection and fluid removal in a well

ABSTRACT

A subassembly is provided which is designed so that two passageways in concentrically arranged tubing strings can be formed to provide a flow-path which in a first direction communicates with equipment at surface in an annular passageway then switches partway along the tubing strings&#39; length in the well to the subassembly and is redirected to the core passageway, and back from the string&#39;s lower end up the annular space to the subassembly and is again redirected this time to the tubing&#39;s core passageway back to surface equipment; the two passageways being: the core passageway formed of the core tubing&#39;s inner volume; and the annular passageway formed of the annular space between the core tubing string and a concentrically surrounding second tubing string&#39;s inner surface; the subassembly forming a two-way cross-over between the two passageways at the same part of the string.

FIELD OF THE INVENTION

In oil and gas production environments, wells often produce gases and liquids, the liquids having a higher density than the gases. If liquids are not produced out of the well's bore, they can accumulate and eventually their weight will act against innate pressure in the well's producing formation, and cause the well's production to slow or stop. Additionally, some produced liquids are valuable commodities, and producers would like to recover them to surface for further processing and sale.

BACKGROUND OF THE INVENTION

Deviated wellbores are a special example of this phenomenon, since an enormous surface area communicating from the production zone to the well's bore is provided along the horizontal section of the wellbore, at roughly the same elevation. This can exacerbate problems with removal of produced liquids, and as well can provide in essence a large bottom-hole reservoir of collected liquids (when compared to a non-deviated well).

DESCRIPTION OF PRIOR ART

In the prior art, quite a few techniques are available to remove fluids from a wellbore, including mechanical pumps, jet pumps, and of particular note, high velocity gas streams achieved by constraining the diameter or carrying volume of a production conduit within a well's bore so that exiting gas is forced to take the low-volume conduit to surface, resulting in a high velocity exit—those systems are aimed at causing the high-velocity exiting gases to carry comingled fluid with the gases in order to produce the fluids in the same high velocity stream.

A variation on that theme, which is proposed for use in a deviated or horizontal well production situation, is disclosed in U.S. Pat. No. 8,006,756 granted to Mazzanti (“Mazzanti '756”). First, Mazzanti '756 contains a discussion of a prior art gas lift system of the prior art in connection with its FIG. 2. Essentially, a narrow conduit or tubing string is inserted into the deviated well terminating at or above the deviation (where the wellbore bends toward horizontal). A packer is deployed to seal the annulus between the well's casing and the outer surface of the narrow conduit. Gas under pressure from surface is flowed down the annulus to above the packer, and can enter the narrow conduit through a gas lift valve. The pressurized gas comingles with fluids which have collected in the well's bore below the packer and upward into the narrowed conduit, and flows to surface bearing comingled fluids with it.

Mazzanti '756 discloses an improved alternative, which provides for injection of pressurized gas into the production zone of the deviated wellbore well beyond the bend to horizontal through the central conduit of a concentrically arranged two-tube system. The outer tube is packed and sealed off to the casing above the bend, and pressurized gas is introduced through the inner conduit to the wellbore below the packer. This pressurized gas together with formation pressure is sufficient to force comingled gas and produced liquids up the well's bore via the annular space between the outer surface of the inner tube and the inner surface of the outer tube of the concentrically arranged tube system. This lift is used to raise liquids to a reservoir above the packer formed of the packer, the well's casing, and the outer surface of the concentrically arranged two-tube system, and then a conventional pump is used to raise liquids to surface. This is a complex multi-stage system.

SUMMARY OF THE INVENTION

The invention includes a subassembly for insertion in a production string inside a cased deviated well to permit the injection of pressurized gas down the annulus (between the outer wall of an inner or core conduit in the tubing and the inner wall of an outwardly concentrically deposed conduit or the wellbore's inner wall) of the string for substantially all of its vertical portion with a passageway communicating in a sealed fashion from the annulus into the central bore at or just below the point where the well is deviated (to horizontal); similarly, fluid flow from the wellbore's lower, deviated portion into the annulus including commingled pressurized gas delivered along the above passageway, flows uphole in that annulus to the crossover sub, where it is directed into the core passage in the tubing string. The advantage is that the higher velocity attained in the vertical portion upward bound more efficiently moves fluids out of the well to surface (including produced fluids) using the pressurized gas introduced during the operation; this occurs with the simultaneous advantage of efficient delivery of the high pressure gas to the lower end of the conduit inside the core tubing, permitting the operation to take place where the outer wall of the annulus is perforated or otherwise open to formation.

In an embodiment, a crossover subassembly is provided for inclusion in a production tubing stream in a well, comprising a body with an upper end with: (i) a first connection to an upper central tube above the body; (ii) a second connection to an annulus between the outer surface of the upper central tube and the inner surface of another conduit, which may be the well's casing or a secondary tubing string; and with a lower end with: (i) a third connection to a lower central tube below the body; and (ii) an opening or fourth connection to an annulus between the outer surface of the lower central tube and the inner surface of another conduit, which may be the well's casing or a secondary tubing string. The subassembly has: at least two passageways through the body: a first passageway communicating between the first connection and the opening or fourth connection; a second passageway communicating between the second connection and the third connection; and a packer or seal between the body and the well's casing or secondary tubing string, to isolate the wellbore above the subassembly from the wellbore below the subassembly.

Another embodiment provides a method for producing fluids from a deviated well with by injecting pressurized gas from surface down a conduit formed of an upper annulus between the outer surface of an upper central tubing string and the inner surface of a second conduit through which the central tubing string is strung, which may be the well's casing or a secondary tubing string from surface equipment to a seal between the outer surface of the upper central tubing string and the inner surface of a cross-over subassembly thus sealing the annulus to the inner wall of the second conduit at the subassembly, then through a passageway through the body of the cross-over subassembly to which the upper annulus is attached at the top of the subassembly in communication through the subassembly to a lower central tubing string extending into the deviated portion of the well's bore and then producing fluids from the deviated portion of the well's bore below the seal on the subassembly's body up the annulus between the inner surface of the well's bore where it is in communication with a formation through which the well was made and the outer surface of the lower central tubing string and then through a second passageway through the subassembly's body into the upper central tubing string and then to surface equipment.

Although the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that modifications and changes may be made while remaining in the scope and spirit of the invention claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram, not to scale, showing flow-paths for introduced gas and produced fluids in a simple deviated wellbore.

FIG. 2 shows a diagram, not to scale, showing mechanical features, conduits and flow directions for introduced gas and produced fluids at the device of the invention (i.e. not “in situ” the well-bore)

FIGS. 3 a and 3 b show a cross-section of two examples of the cross-over subassembly of the invention.

DETAILED DESCRIPTION

When lifting fluids from a horizontal well's horizontal portion of its bore, typically where the bore is open to production, using pressurized gas lift with gas under pressure from surface introduced to the well, it is desirable that the pressurized gas be delivered as deeply into the well as possible to mix and comingle with fluids collected in the bore for as much distance in the bore as possible. Since the well's bore may be open to the production zone over much of its length, this means it is desirable to have the pressurized gas delivered in a conduit such as a tube, and not in the annulus between a tubing string and the well's bore's face.

In this invention, in the deviated (horizontal) part of the well's bore we deploy a conduit 10 with its open bottom end 20 in communication with the wellbore 90 within its horizontal or deviated portion. Conduit 10 is at its top end 30 connected to and in communication with the crossover subassembly 50. In operation, the crossover subassembly 50 will be sealed with a packer 55 to the casing 110 of the vertical portion of the wellbore (or to some functionally equivalent tubing string if the well has multiple completions—not shown). Within the crossover subassembly 50, a passageway 60 which communicates with conduit 10 also communicates with the annular space above the packer 55 between the casing 110 and another tubing 70 to surface equipment (not shown). Similarly, a passageway 65 communicates between an upper tubing 70 and the annulus between the wellbore 90 and the outer surface of the lower conduit 10 below packer 55.

As can be seen, high pressure gas from surface (downward arrows 80) flow from surface equipment (not shown) down the annulus between casing 110 and conduit 70 through packer 55 and subassembly 50 into conduit 10, and then out the lower end of conduit 10 into the wellbore. There, the pressurized gas comingles with fluids in the horizontal portion of the wellbore 90 and flow toward surface in the annulus between the wellbore 90 and the outer surface of tubing 10, into the subassembly 50 past packer 55 and into the upper conduit 70 (shown by arrows 85) to collection facilities at surface (not shown). This accomplishes two things: delivery of pressurized gas well into the horizontal portion of the wellbore 90, and delivery up the vertical portion of the production string at high velocities in small-diameter tubing 70. 

1. A crossover subassembly for inclusion in a production tubing stream in a well, comprising a body with i. An upper end with:
 1. A first connection to an upper central tube above the body
 2. A second connection to an annulus between the outer surface of the upper central tube and the inner surface of another conduit, which may be the well's casing or a secondary tubing string ii. A lower end with:
 1. A third connection to a lower central tube below the body; and
 2. An opening or fourth connection to an annulus between the outer surface of the lower central tube and the inner surface of another conduit, which may be the well's casing or a secondary tubing string iii. At least two passageways through the body, comprising:
 1. A passageway communicating between the first connection and the opening or fourth connection; and
 2. A second passageway communicating between the second connection and the third connection iv. And a packer or seal between the body and the well's casing or secondary tubing string, to isolate the wellbore above the subassembly from the wellbore below the subassembly
 2. A method for producing fluids from a deviated well with by: a. injecting pressurized gas from surface down a conduit formed of: i. An upper annulus between the outer surface of an upper central tubing string and the inner surface of a second conduit through which the central tubing string is strung, which may be the well's casing or a secondary tubing string from surface equipment to a seal between the outer surface of the upper central tubing string and the inner surface of a cross-over subassembly thus sealing the annulus to the inner wall of the second conduit at the subassembly ii. A passageway through the body of the cross-over subassembly to which the upper annulus is attached at the top of the subassembly in communication through the subassembly to a lower central tubing string extending into the deviated portion of the well's bore b. Producing fluids from the deviated portion of the well's bore below the seal on the subassembly's body along a route comprising: i. up the annulus between the inner surface of the well's bore where it is in communication with a formation through which the well was made and the outer surface of the lower central tubing string ii. through a second passageway through the subassembly's body into the upper central tubing string and then to surface equipment
 3. The method of claim 2 where the subassembly is sealed to the well's casing at or near the bottom of the well's vertical portion and before its deviated or horizontal portion. 